This invention relates to an electrical connector and more particularly to a low insertion force connector having a contact arrangement which provides a good electrical contact for printed circuit boards having beveled edges.
In many systems and for a variety of reasons, many electronic elements, components, circuitry, and interconnections are presently mounted, deposited, printed, or otherwise formed on one or both sides of a board (a printed circuit board, PCB) or other suitable substrate. Electrical interconnections of the PCB or the like and a backpanel or the like of the system are generally accomplished by a connector.
These connectors generally include a housing which is bolted or otherwise affixed to the backpanel, and the housing is formed with a longitudinal slot for receiving one edge of the printed circuit board or the like. The connector is provided with a plurality of individual interconnection elements each of which is adapted to suitably contact the backpanel on one end, and to suitably contact the printed circuit board or the like on the other end. The electrical connections provided by these interconnection elements are formed in various well known manners with the connections to the backpanel being relatively permanent in comparison to the connections made with the printed circuit board or the like.
In many connector configurations, the interconnection elements are formed so that one end of each interconnection element protrudes through the backpanel and wire-wrapped or otherwise connected. Connections between the interconnection element and the PCB or the like are generally made by mechanically biasing the interconnection elements of the connector into engagement with the edge contacts of the printed circuit board or the like. This mechanical biasing force serves two purposes, the first being to provide the electrical connections and the second being to grip the printed circuit board or the like, and thus hold the PCB or the like in the connector. It should be apparent that the biasing force exerted by the interconnecting elements must be relatively high to insure that good conductive contacts are made and maintained. The high biasing force causes a high insertion force of the PCB or the like which becomes excessive when the number of the interconnection elements of the connector is of a large quantity, the problem of the high insertion force being the impetus behind the development of zero insertion force and low insertion force connectors.
Another problem with these connectors is that the contact areas of the edge contacts and the interconnecting elements will rub against each other with considerable force during insertion and removal of the printed circuit board or the like. Since the edge contacts of a typical printed circuit board are only a few thousandths of an inch thick, this rubbing action which occurs during insertion and removal of the printed circuit board tends to wear away the edge contacts and may well ruin a PCB after several insertions and removals. This rubbing action may also wear away high-cost precious metal on the surface of the interconnecting elements which invites poor electrical contacts or corrosion and can result in hard to detect failures of the equipment.
In view of these above stated problems several attempts have been made to produce what has become known in the art as zero or low insertion force connector. Generally, these zero or low insertion force connectors are provided with mechanical actuating mechanisms which move the contact area of the interconnections elements out of the insertion and removal path of the printed circuit board or the like and allow the interconnecting elements to move into engagement with the edge contacts after the printed circuit board or the like has been inserted. Such a zero or low insertion force connector is disclosed in U.S. Pat. No. 4,355,856, issued Oct. 26, 1982, entitled "Low Insertion Force Connector Using Non-Noble Metal Contact Plating," by Warren W. Porter, and assigned to the same assignee as the present application. The referenced Patent discloses an actuating mechanism which is activated by the insertion of a printed circuit board or the like causing interconnecting elements to move and make contact with edge contacts of the printed circuit board, resulting in a low insertion force connector and eliminating any rubbing or wiping action between the edge contacts of the printed circuit board and the interconnecting elements, the interconnecting elements having sharp edges for piercing the oxide layer of the edge contact thus forming good electrical contacts. However, when this connector is utilized in conjunction with a printed circuit board having beveled edges, a high probability exists that the connector will not operate correctly, i.e., the interconnection elements will not properly engage or make contact with the edge contacts of the printed circuit board because the edge contacts do not extend to the end of the printed circuit board but only to the start of the beveled edge.
Therefore, a need exists for a new and improved zero or low insertion force connector which allows the use of a printed circuit board having beveled edges, in addition to a printed circuit board having non-beveled edges, and simultaneously offers the advantages of the connector of the aforementioned U.S. Pat. No. 4,355,856.